Flow Structure
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2022 ◽  
pp. 1-24
Author(s):  
Jordi Ventosa-Molina ◽  
Björn Koppe ◽  
Martin Lange ◽  
Ronald Mailach ◽  
Jochen Fröhlich

Abstract In turbomachines, rotors and stators differ by the rotation of the former. Hence, half of each stage is directly influenced by rotation effects. The influence of rotation on the flow structure and its impact on the performance is studied through Wall-Resolving Large Eddy Simulations of a rotor with large relative tip gap size. The simulations are performed in a rotating frame with rotation accounted for through a Coriolis force term. In a first step experimental results are used to provide validation. The main part of the study is the comparison of the results from two simulations, one representing the rotating configuration, one with the Coriolis force removed, without any other change. This setup allows very clean assessment of the influence of rotation. The turbulence-resolving approach ensures that the turbulent flow features are well represented. The results show a significant impact of rotation on the secondary flow. In the tip region the Tip Leakage Vortex is enlarged and destabilised. Inside the tip gap the flow is altered as well, with uniformization in the rotating case. At the blade midspan, no significant effects are observed on the suction side, while an earlier transition to turbulence is found on the pressure side. Near the hub, rotation effects are shown to reduce the corner separation significantly.


2022 ◽  
Vol 16 (2) ◽  
pp. 29-40
Author(s):  
S. A. Akinin ◽  
A. V. Starov

The results of computational and experimental studies of a model of a hypersonic convergent air intake are presented. Experimental studies were carried out in a hot-shot wind tunnel IT-302M SB RAS at a Mach number M = 5.7 and an angle of attack α = 4 °. Numerical modeling was carried out in a three-dimensional setting in the ANSYS Fluent software package. The calculations were carried out in 4 versions using different turbulence models: k-ɛ standard, RNG k-ɛ, k-ɷ standard and k-ɷ SST. The features of the flow structure are established. The pressure distributions on the compression surfaces and in the air intake channel are obtained. The separated flow at the entrance of the inner channel was studied. It was found that the use of various turbulence models has a significant effect on the size and position of separation. The best agreement between the calculated and experimental data on the level of static pressure was shown by the variant with the k-ɛ standard turbulence model.


2022 ◽  
pp. 1-44
Author(s):  
Yong Luan ◽  
Yu Rao ◽  
Kai Wang ◽  
Weilong Wu

Abstract This paper presents a comparative experimental and numerical study of the heat transfer and pressure loss in a swirl multi-pass channel with tangential jet slots, and another baseline multi-pass channel with 180-deg U-bends as comparison baseline has also been investigated. Transient liquid crystal thermography is used to obtain the detailed heat transfer distribution on the internal surfaces of the multi-pass serpentine channels. The heat transfer patterns in the swirl multi-pass channel are quite different from that of the baseline multi-pass channel. Compared with the baseline multi-pass channel, the experimental globally averaged Nusselt number ratios of the last two passes in the swirl multi-pass channel can be increased by up to 82.9%, 104.8% and 124.6% for the Reynolds numbers 20,000, 40,000 and 60,000, respectively. The high and circumferentially uniform heat transfer is mainly due to the large-scale swirling flow induced by the tangential slots. More detailly, the large-scale swirling flow impinges onto the surface and further induces high tangential velocity near the wall, which destroys the boundary layer flow and thus improves the heat transfer rates at the wall. However, the notable pressure loss of the swirl multi-pass channel should be further controlled reasonably, which is about 5.4 times that of the baseline multi-pass channel. As supplements to the experiments, three-dimensional numerical computations provide more insights into the turbulent flow structure in the two kinds of multi-pass serpentine channels.


Encyclopedia ◽  
2022 ◽  
Vol 2 (1) ◽  
pp. 56-69
Author(s):  
Sibo Li ◽  
Roberto Paoli

Aircraft icing refers to the ice buildup on the surface of an aircraft flying in icing conditions. The ice accretion on the aircraft alters the original aerodynamic configuration and degrades the aerodynamic performances and may lead to unsafe flight conditions. Evaluating the flow structure, icing mechanism and consequences is of great importance to the development of an anti/deicing technique. Studies have shown computational fluid dynamics (CFD) and machine learning (ML) to be effective in predicting the ice shape and icing severity under different flight conditions. CFD solves a set of partial differential equations to obtain the air flow fields, water droplets trajectories and ice shape. ML is a branch of artificial intelligence and, based on the data, the self-improved computer algorithms can be effective in finding the nonlinear mapping relationship between the input flight conditions and the output aircraft icing severity features.


2022 ◽  
Author(s):  
Yoo-Jin Ahn ◽  
Mustafa N. Musta ◽  
Marc A. Eitner ◽  
Jayant Sirohi ◽  
Noel T. Clemens

Flow ◽  
2022 ◽  
Vol 2 ◽  
Author(s):  
Jennifer L. Cardona ◽  
John O. Dabiri

Abstract This work explores the relationship between wind speed and time-dependent structural motion response as a means of leveraging the rich information visible in flow–structure interactions for anemometry. We build on recent work by Cardona, Bouman and Dabiri (Flow, vol. 1, 2021, E4), which presented an approach using mean structural bending. Here, we present the amplitude of the dynamic structural sway as an alternative signal that can be used when mean bending is small or inconvenient to measure. A force balance relating the instantaneous loading and instantaneous deflection yields a relationship between the incident wind speed and the amplitude of structural sway. This physical model is applied to two field datasets comprising 13 trees of 4 different species exposed to ambient wind conditions. Model generalization to the diverse test structures is achieved through normalization with respect to a reference condition. The model agrees well with experimental measurements of the local wind speed, suggesting that tree sway amplitude can be used as an indirect measurement of mean wind speed, and is applicable to a broad variety of diverse trees.


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